Connecticut
Pre-proposal to the United States Environmental Protection Agency
Innovations Grant Program
August 19, 2002
Submitted by
Connecticut Department of Environmental Protection
Bureau of Water Management
79 Elm Street
Hartford, CT 06106-5127
Monitoring of Municipal Sewage Treatment Plants For Pollutant Credit Exchange and Compliance
Summary
The Connecticut Department of Environmental Protection (DEP)
is implementing legislation authorizing the issuance of a watershed general
permit to regulate the discharge of nitrogen from municipal point sources
and the institution of a nitrogen credit-trading program pursuant to the
approved Total Maximum Daily Load (TMDL) for Long Island Sound. The General
Permit (GP) issued by DEP regulates 79 publicly-owned wastewater treatment
works (POTW) located throughout the state of Connecticut and establishes
the most expansive program of water pollutant trading in the U.S. This
program is projected to save the state $200 million in capital construction
costs and will accelerate the schedule for meeting the TMDL wasteload
allocation (WLA) for point sources by providing economic incentives for
those POTWs that move quickly to remove nitrogen and comply with the limits
in the GP. There is potential to expand this approach within Connecticut
to other sources, including nonpoint sources. It can also serve as a model
for other states that are facing similar TMDL implementation challenges
not only as a cost-effective approach to reducing a pollutant from numerous
sources, but also as an innovative approach to integrating the allocation
of State Revolving Fund funding with permitting and enforcement programs.
Despite the anticipated value and cost savings from implementing the Nitrogen Credit Exchange (NCE) in Connecticut, there are concerns over the reliability and accuracy of standard monitoring protocols. The GP sets monitoring frequency based on plant size. Facilities with design flows greater than or equal to 10 MGD are required to monitor the final effluent at a minimum frequency of twice per week while smaller plants are required to monitor at a minimum of once per week. Each sample must be a 24-h composite sample and be analyzed according to methods approved by EPA. While it is believed that this frequency will be adequate to characterize an individual plant's nitrogen load and that analytical protocols are proven suitable for wastewater analysis, local plant variability and weather effects may produce enough statistical error to require additional analyses. There have been no detailed studies of effluent nitrogen variability on daily to weekly time scales at Connecticut facilities. Given the economic impact of the nitrogen trading program at municipal and state levels, DEP needs to provide assurance that monitoring to generate credits is reasonably accurate and conducted at the most cost-effective frequency possible. Further, this evaluation will assist scheduling of compliance checks and reduce the possibility that nitrogen loads to Long Island Sound are erroneously under reported.
Background
Over the past decade, DEP has worked with the EPA Long Island Sound Study
(LISS) and the Water Environment Research Foundation (WERF) to develop
a framework for a Nitrogen Credit Trading Program. Connecticut and New
York jointly drafted the TMDL to address seasonal low oxygen problems
in Long Island Sound and with its approval in early 2001, Connecticut
is faced with reducing nitrogen loads from 79 POTWs scattered throughout
the state. Nitrogen is the primary pollutant linked to an extensive low-oxygen
(hypoxia) problem that affects up to half of Long Island Sound's 1300
square miles of bottom during periods of summer stratification when bottom
waters are prevented from mixing with surface waters. The nitrogen fuels
the growth of algae, which eventually decays after it settles to the bottom
of the Sound. The Sound is so heavily enriched that the microbial decay
drives oxygen to levels low enough to create unhealthy or even lethal
conditions for aquatic life.
The TMDL1 to correct this problem, which was approved by the EPA in April 2001, requires a 58.5% reduction in baseline anthropogenic nitrogen loads from sources in Connecticut and New York by the year 2014. Using the trading framework developed by the LISS and WERF2 as a starting point, DEP proposed legislation3 to establish a nitrogen general permit and a nitrogen credit-trading program for municipal point sources throughout Connecticut. Public Act 01-180 was passed in June 2001 and established a Nitrogen Credit Exchange (NCE) to be guided by a Nitrogen Credit Advisory Board (NCAB) under the authority of the Commissioner of the DEP.
The Nitrogen General Permit is key to the success of Connecticut's trading program. It collectively regulates 79 POTWs located throughout the state and establishes the basis for the most expansive program of water pollutant trading in the U.S. The GP sets annual nitrogen limits for each POTW that are increasingly stringent until the final WLA is attained in 2014. POTWs can comply by either treating or by purchasing credits from the Nitrogen Credit Exchange annually. The nitrogen credit-trading program is both innovative and essential to resolve the complex water quality problems in Long Island Sound in a cost-effective manner. The proposed program links together Connecticut's existing general permitting authorities, the State Revolving Loan Program (SRF) and other salient features of state and federal laws to form a comprehensive regulatory program to assure compliance with Connecticut's nitrogen reduction requirements under the TMDL. However, the success or failure of this program, and the improvement to the health of LIS, rely heavily on our ability to accurately monitor nitrogen loads from the 79 facilities incorporated in the GP.
TASK 1
The first task under this proposal would be to conduct high-intensity
monitoring at four to six municipal POTWs representing a range of sizes,
nitrogen removal capability, and susceptibility to weather changes (e.g.,
infiltration from wet conditions). Samples would be collected at the facilities
by automatic sampler for later analysis. One larger facility would be
selected to utilize online real-time nitrogen analysis systems. The real-time
analysis system will be installed and operated for a period of one year.
The facility utilizing the online real real-time system would also conduct
the same high-intensity monitoring. Laboratory analyses would be conducted
using EPA standard protocols under an approved EPA Quality Assurance Project
Plan (QAPP). Frequency would be at least four times per day over a two-week
period once during each of four seasons. This sampling strategy would
experience a full range of wet/dry and warm/cool conditions that might
affect nitrogen removal capability, and would also fully examine day to
day fluctuations in effluent nitrogen strength.
Data would be analyzed statistically to identify and develop a sampling scheme that would maximize precision in monthly nitrogen load calculations. It is possible that certain conditions might need to be targeted for more frequent sampling, such as higher spring flows that might vary with rainfall, or certain days of the week that might reflect maximum or minimum concentrations related to business days vs. weekend conditions. The data could also help guide compliance monitoring programs to ensure reliable, yet cost-effective checks on self-monitoring programs. In both cases, it is the desire of DEP to gain the most reliable nitrogen load estimations with the minimum resources, saving money for the municipalities and DEP while not compromising the credibility of the NCE.
TASK 2
In addition to the first year's assessment of monitoring, DEP proposes
to evaluate the program's effectiveness in regulating point source discharges
as related to the accuracy of nitrogen load estimates. Because the first
year of operation of the NCE (2002) will be based on the requirements
of the GP noted above, this monitoring study will allow estimates of error
under GP protocols compared to proposed revisions in the monitoring program
that the study might support. Since one possibility is that the GP monitoring
requirements are excessive, it will also be possible to demonstrate what
significance there might be to an increase in sampling error under a reduced
sampling schedule. Any number of "what if" scenarios can be constructed
using the database generated in this study, allowing an optimal monitoring
program to be selected from a range of potential error conditions.
TASK 3
The third task would seek to maximize efficiency of quality assurance
for individual facility monitoring programs (e.g., duplicates, blanks)
and frequency of independent (e.g., DEP) split sampling or compliance
sampling. This analysis of the data would focus on error in split and
duplicate samples, perhaps using two labs for some of the analyses, to
ascertain level of reliability at the facility level and increase value
of compliance sampling at the state level. An attempt will also be made
to identify attributes associated with unreliable data or operational
problems leading to development of a "risk-based" compliance/technical
assistance program.
Broader Application
Connecticut has embarked on a complex, but highly innovative, general
permitting and trading program that has not been implemented to this degree
anywhere else in the U.S. Of prime consideration in evaluating the success
of the point source program being implemented in 2002 and the potential
for change in sampling frequency and timing, including compliance sampling
without compromising nitrogen load estimation accuracy. In addition is
the learning value it may hold for other states implementing complex TMDLs
that require accurate reporting of pollutant loads. Estuaries like the
Chesapeake Bay and Gulf of Mexico are addressing hypoxia problems similar
to those observed in Long Island Sound and are planning and implementing
nutrient control programs in multi-state areas. The successes and failures
of Connecticut's program will yield valuable lessons for these and other
areas where closed system trading under a general permit makes economic
and environmental sense and the credibility of the program relies on accurate
monitoring of effluent parameters.
Deliverables
Final products of this project will include:
- A technical assessment of the intensive monitoring effort along with a comparative analysis of utilization of online real-time nitrogen analysis. (Task 1)
- An evaluation of the change in error related to a range of monitoring schedules (Task 2)
- An evaluation of quality assurance sampling and compliance sampling (Task 3)
Budget (estimated for a two-year study effort) [REDACTED BY US EPA]
References
- New York State Department of Environmental Conservation and Connecticut Department of Environmental Protection. 2000. A total maximum daily load analysis to achieve water quality standards for dissolved oxygen in Long Island Sound. NYSDEC and CTDEP, 57 p.
- Water Environment Research Foundation. 1999. Nitrogen credit trading for Long Island Sound watershed. R.E. Moore, M.S. Overton, R.J. Norwood and D. DeRose, PIs. WERF Final Report RFP 97-IRM-5.
- Substitute Senate Bill No. 1012. 2001. An act concerning nitrogen reduction in Long Island Sound, Public Act No. 01-180. Connecticut General Assembly.
- General Permit for Nitrogen Discharges